refactor(@angular/cli): allow tty and color helpers to use a stream

The `isTTY` and `supportColor` helpers can now accept a stream to check
instead of assuming stdout. This is useful if stderr needs to be checked,
for instance. Also, color checking now uses Node.js `hasColors` where
possible which has been available since Node.js v10.

Author: clydin

packages/angular/cli/src/utilities/color.ts

@@ -10,29 +10,15 @@ import { WriteStream } from 'node:tty';
 
 export { color as colors, figures } from 'listr2';
 
-export function supportColor(): boolean {
-  if (process.env.FORCE_COLOR !== undefined) {
-    // 2 colors: FORCE_COLOR = 0 (Disables colors), depth 1
-    // 16 colors: FORCE_COLOR = 1, depth 4
-    // 256 colors: FORCE_COLOR = 2, depth 8
-    // 16,777,216 colors: FORCE_COLOR = 3, depth 16
-    // See: https://nodejs.org/dist/latest-v12.x/docs/api/tty.html#tty_writestream_getcolordepth_env
-    // and https://github.com/nodejs/node/blob/b9f36062d7b5c5039498e98d2f2c180dca2a7065/lib/internal/tty.js#L106;
-    switch (process.env.FORCE_COLOR) {
-      case '':
-      case 'true':
-      case '1':
-      case '2':
-      case '3':
-        return true;
-      default:
-        return false;
-    }
+export function supportColor(stream: NodeJS.WritableStream = process.stdout): boolean {
+  if (stream instanceof WriteStream) {
+    return stream.hasColors();
   }
 
-  if (process.stdout instanceof WriteStream) {
-    return process.stdout.getColorDepth() > 1;
+  try {
+    // The hasColors function does not rely on any instance state and should ideally be static
+    return WriteStream.prototype.hasColors();
+  } catch {
+    return process.env['FORCE_COLOR'] !== undefined && process.env['FORCE_COLOR'] !== '0';
   }
-
-  return false;
 }

packages/angular/cli/src/utilities/tty.ts

@@ -11,12 +11,12 @@ function _isTruthy(value: undefined | string): boolean {
   return value !== undefined && value !== '0' && value.toUpperCase() !== 'FALSE';
 }
 
-export function isTTY(): boolean {
+export function isTTY(stream: NodeJS.WriteStream = process.stdout): boolean {
   // If we force TTY, we always return true.
   const force = process.env['NG_FORCE_TTY'];
   if (force !== undefined) {
     return _isTruthy(force);
   }
 
-  return !!process.stdout.isTTY && !_isTruthy(process.env['CI']);
+  return !!stream.isTTY && !_isTruthy(process.env['CI']);
 }